Temperatures below the freezing point of water —0 degrees Celsius, otherwise described as −32 degrees Fahrenheit—cause liquid water to tum solid. Since living organisms are comprised mostly of liquid water, the exposure to external temperatures below the freezing point is dangerous. After lengthy exposure to a below freezing temperature, the liquids within the body will begin to solidify and damage the biological cells. Also, in nature, physiological solutes whose solubilities change dramatically with temperature changes may crystallize or solidify in body fluids, which can be lethal. This may damage the organism and lead to death of the organism.
Trehalose is a multifunctional non-reducing disaccharide, occurring naturally in all biological kingdoms. In addition to being an energy and carbon source, this sugar protects cells and proteins against injuries in extreme environments, prevents osteoporosis, alleviates certain diseases, and acts as a signal molecule in plants. Due to its superior bioprotective properties, trehalose has a wide range of applications in industries (e.g., medical, pharmaceutical, and food industries). For examples, trehalose can be used as an additive in foods to maintain moisture and/or the stabilities of other food components; trehalose can be included in formulations of drugs and vaccines to pertain the stability and functions of active pharmaceutical ingredients; trehalose can also be used as a cryoprotectant.
However, the solubility of trehalose decreases dramatically with the decrease of temperature and its hydrate has even lower solubility than trehalose. Thus, trehalose is prone to precipitation or crystallization out of the solutions or formulations, in particular, at low temperatures, to form trehalose dihydrate. Trehalose's high propensity to precipitation or crystallization significantly limits its applications as such precipitation/crystallization can greatly impair the protection effectiveness of trehalose as well as the quality of the final products. Therefore, an effective and environmentally friendly additive for preventing trehalose precipitation/crystallization is needed.
Antifreeze Proteins (“AFP's”) in cold-adapted organisms including fish, insects, plants, bacteria, fungi bind to specific surfaces of ice crystals to inhibit their growth of ice in vivo. AFPs depress the freezing point of water without appreciably altering the melting point leading to a difference between the melting point and the freezing point, referred to as thermal hysteresis (TH, a measure of antifreeze activity). AFPs in freeze-avoiding species prevent them freezing. However, AFPs are also present in freeze-tolerant species at levels too low to produce significant antifreeze activity, causing speculation of their role in freeze-tolerant species. More recently, AFPs role in controlling the formation of other types of crystals, such as nucleosides, has been also reported.